clutch LAND ROVER DEFENDER 1999 Owner's Guide

33CLUTCH
12
DESCRIPTION AND OPERATION OPERATION
Hydraulic operation
When the clutch pedal is depressed, the master cylinder piston is pushed into the master cylinder. The movement
of the piston pressurises the fluid in the master cylinder, forcing the pressurised fluid into the hydraulic feed pipe to
the slave cylinder. The hydraulic pressure is felt at the slave cylinder piston which moves under the hydraulic force
applied, pushing the clutch release lever via the piston rod.
When the clutch pedal is released, the force applied to the release lever by the fingers of the diaphragm, moves
the release lever, which pushes the slave cylinder piston into the cylinder. The displaced hydraulic fluid is pushed
up the hydraulic feed pipe and returns to the master cylinder.
Mechanism operation
When the clutch pedal is depressed, hydraulic pressure extends the piston and rod in the slave cylinder. The
extension of the piston pushes the rod against the outer end of the release lever which pivots around the ball
spigot.
The inner end of the release lever pivots towards the engine applying pressure to the release bearing. The release
bearing slides along the release bearing sleeve and pushes on the fingers of the diaphragm. The diaphragm
pivots around the chamfered rivets in the cover. As the diaphragm is deflected, it removes pressure from the
pressure plate. The pressure plate moves away from the drive plate assisted by the three leaf springs.
The removal of force from the pressure plate on the drive plate reduces the friction between the dual mass
flywheel, drive plate and pressure plate. The drive plate slips between the flywheel and the pressure plate
preventing rotary movement being transferred from the flywheel and pressure plate to the primary driveshaft.
When the clutch pedal is released, hydraulic force is removed from the piston in the slave cylinder. This allows the
fingers of the diaphragm to push the release bearing along the release bearing sleeve. The movement of the
release bearing moves the release lever which pivots on the ball spigot, pushing the piston and rod back into the
slave cylinder.
The removal of pressure from the release bearing on the diaphragm, causes the diaphragm to pivot around the
chamfered rivets in the cover. The force applied to the pressure plate from the diaphragm overcomes the force of
the leaf springs and the pressure plate moves towards the drive plate and flywheel.
The pressure plate applies pressure to the drive plate which is pushed against the flywheel. As the clutch pedal is
progressively released, the friction between the drive plate, flywheel and pressure plate increases. The increase in
friction transfers the rotary movement of the flywheel and pressure plate to the drive plate, which in turn starts to
rotate the primary drive shaft. When the clutch pedal is released fully, the force applied by the diaphragm to the
pressure plate forces the drive plate onto the flywheel with no slippage.
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CLUTCH
1
ADJUSTMENT HYDRAULIC SYSTEM - BLEED
Service repair no - 33.15.01
Check
CAUTION: Ensure the fluid in the reservoir
is maintained between the minimum and
maximum levels throughout the bleed
procedure using new brake fluid.
CAUTION: Brake fluid will damage paint
finished surfaces. If spilled, immediately
remove fluid and clean area with water.
1.Top up clutch system reservoir.
2.Raise front of vehicle and support on stands.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
3.Remove dust cap, connect bleed tube to bleed
screw and submerge free end into a clear
container of brake fluid.
4.Loosen bleed screw, then apply steady pressure
to the clutch pedal, depressing it through its full
stroke. Allow the pedal to return unassisted.
5.Repeat the procedure until a flow of clean,
air-free fluid is purged into the container.
6.Hold pedal down and tighten bleed screw to9
Nm (7 lbf.ft).
7.Check and top up reservoir.
CAUTION: Never re-use fluid that has been
bled from the system.
8.Remove stands and lower vehicle.
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CLUTCH
1
REPAIR CLUTCH ASSEMBLY
Service repair no - 33.10.01.01
Remove
1.Remove gearbox assembly.See MANUAL
GEARBOX, Repair.
2.Restrain flywheel.
3.Working in sequence, loosen 6 nuts securing
clutch cover to flywheel.
4.Remove clutch cover and clutch plate.
Refit
5.Clean clutch cover and flywheel mating faces
and spigot bush in end of crankshaft.
6.Position clutch drive plate to flywheel with
’gearbox side’ facing towards gearbox.
7.PositionLRT-12-152alignment tool through
drive plate into spigot bearing in crankshaft.8.Fit clutch cover and locate on dowels.
9.Position clutch cover nuts and tighten in diagonal
sequence to25 Nm (18 lbf.ft).
10.Fit gearbox assembly.See MANUAL
GEARBOX, Repair.
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33CLUTCH
2
REPAIR BEARING - CLUTCH RELEASE
Service repair no - 33.25.12
Remove
1.Remove gearbox assembly.See MANUAL
GEARBOX, Repair.
2.Remove retaining peg and remove release
bearing.
3.Remove bolt securing clutch release fork,
remove retaining clip and remove clutch release
fork.
Refit
4.Clean release fork.
5.Examine clutch release fork pivot points for
wear.
6.Apply a smear of Molybdenum disulphide grease
to release fork pivot points.
7.Fit retaining clip ensuring it locates over pivot
point washer.
8.Fit bolt and tighten to10 Nm (7 lbf.ft).
9.Clean release bearing and bearing sleeve
mating faces.
10.Apply smear of Molybdenum disulphide grease
to release bearing sleeve.
11.Fit release bearing and secure with retaining
peg.
12.Fit gearbox assembly.See MANUAL
GEARBOX, Repair.CLUTCH - MASTER CYLINDER LH DRIVE
Service repair no - 33.20.01
Remove
1.Remove 3 screws securing closing panel to
lower’A’post.
2.Release closing panel sufficient to gain access
to clutch and brake pedal bracket bolts.
3.Remove clutch pedal rubber.
4.Remove 12 bolts securing clutch and brake
pedal brackets to body.
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CLUTCH
3
REPAIR
5.Disconnect multiplug from clutch pedal sensor.
6.Disconnect muliplug and harness clip from pedal
bracket.
7.Position cloth to collect fluid spillage.
8.Loosen pipe union, release pipe and plug pipe
and master cylinder.
9.Move brake master cylinder assembly aside and
lift out clutch master cylinder assembly.
10.Remove 6 screws, remove pedal box top cover
and discard gasket.
11.Remove nut securing push rod to clutch pedal
trunnion.
12.Remove 2 bolts and remove clutch master
cylinder from pedal bracket.
13.Remove clutch pedal sensor and pipe union
from master cylinder and discard sealing
washers.Refit
14.Clean sensor and pipe union.
15.Fit clutch pedal sensor and pipe to master
cylinder using new sealing washers.
16.Position master cylinder to pedal bracket and
align push rod to pedal trunnion.
17.Fit bolts and nuts and secure master cylinder to
pedal bracket.
18.Fit nut securing push rod to clutch pedal trunnion
but do not tighten nut at this stage.
19.Move brake master cylinder aside and position
clutch master cylinder assembly.
20.Clean clutch pipe union.
21.Align pipe and tighten union.
22.Connect multiplug to clutch pedal sensor.
23.Tighten bolts securing clutch pedal and brake
pedal brackets to body.
24.Fit clutch pedal rubber.
25.Position closing panel and tighten screws to
lower’A’post.
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33CLUTCH
4
REPAIR Clutch pedal setting
1.Loosen both locknuts on master cylinder push
rod.
2.Check distance from lower edge of clutch pedal
to floor. Correct measurement is 140 mm (5.50
in) without floor mat.
3.Adjust pedal stop to obtain correct setting.
4.Adjust master cylinder push rod to obtain
approximately 1.5 mm (0.06 in) free play
between push rod and master cylinder piston.
5.Tighten push rod locknuts.
6.Check operation of clutch pedal and ensure that
there is minimum of 6 mm (0.25in) of free play
before pressure is felt.
7.Fit pedal box top cover and multiplug bracket
using a new gasket and secure with screws.
8.Connect multiplug and harness clip to pedal
bracket.
9.Bleed clutch hydraulic system.See
Adjustment.CYLINDER - CLUTCH SLAVE
Service repair no - 33.35.01
Remove
1.Disconnect pipe from slave cylinder.
CAUTION: Plug the connections.
2.Position container to catch spillage.
3.Remove 2 bolts securing slave cylinder to bell
housing.
4.Withdraw slave cylinder from bell housing and
push rod.
Refit
5.Clean ends of pipes, bell housing and slave
cylinder mating faces.
6.Lubricate end of push rod with Molybdenum
disulphide gease.
7.Locate slave cylinder to push rod and bell
housing.
8.Fit bolts and tighten to25 Nm (18 lbf.ft).
9.Connect clutch pipe to slave clyinder.
10.Bleed clutch system.See Adjustment.
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MANUAL GEARBOX
1
REPAIR COVER - FRONT - RESEAL AND FIT NEW INPUT
SHAFT OIL SEAL
Service repair no - 37.12.33.01
Remove
1.Remove gearbox.See this Section.
2.Remove retaining peg and remove release
bearing.
3.Remove bolt securing clutch release fork,
remove retaining clip and remove clutch release
fork.
4.Remove 2 bolts securing release bearing sleeve,
remove bearing sleeve.
5.Remove 6 bolts securing clutch housing, remove
housing.
6.Remove and discard 6 bolts securing front
cover, remove cover.
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37MANUAL GEARBOX
2
REPAIR
7.Using a soft metal drift, carefully remove input
shaft front bearing track from front cover.
CAUTION: Take care not to damage
bearing track, if track is damaged, it will be
necessary to fit a new input shaft front
bearing.
8.Remove input shaft oil seal from front cover;
discard oil seal.
Refit
9.Using a suitable solvent clean seal recess, front
cover and gearbox mating faces; clean threads
of bolts and bolt holes.
10.Clean bearings and bearing races.
11.Lubricate a new oil seal with gearbox oil.
12.Fit oil seal using a suitable mandrel.
13.Fit input shaft front bearing track using a press
and suitable mandrel.
14.Apply sealant, Part No. STC 4404 to front cover.
15.Position front cover, apply Loctite 290 to threads
of bolts; fit new bolts and tighten by diagonal
selection to25 Nm (18 lbf.ft).
16.Clean clutch housing mating faces, dowels and
dowel holes.
17.Position clutch housing, fit bolts and tighten by
diagonal selection to75 Nm (55 lbf.ft).
18.Clean bearing sleeve mating faces, dowel and
dowel holes.
19.Position bearing sleeve, fit bolts and tighten to
25 Nm (18 lbf.ft).
20.Examine clutch release fork pivot points for wear
and replace as required.
21.Apply a smear of Molybdenum disulphide grease
to pivot points and position release fork.
22.Fit retaining clip ensuring it locates over pivot
point washer, fit bolt and tighten to10 Nm (7
lbf.ft).23.Clean release bearing and bearing sleeve
mating faces.
24.Apply smear of Molybdenum disulphide grease
to release bearing sleeve.
25.Fit release bearing and secure with retaining
peg.
26.Fit gearbox.See this Section.
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37MANUAL GEARBOX
8
REPAIR
12.Remove 13 screws securing tunnel cover.
13.Release and remove tunnel cover.
14.Remove cooling fan.See COOLING SYSTEM,
Repair.
15.Remove air filter.See FUEL SYSTEM, Repair.
16.Remove 2 upper bolts securing clutch housing to
engine.
17.Remove bolt securing shim to clutch housing.
18.Release gearbox breather pipes from clips on
heater hose.
19.Remove starter motor.See ELECTRICAL,
Repair.
20.Remove exhaust front pipe.See MANIFOLD
AND EXHAUST SYSTEM, Repair.
21.Drain gearbox oil.See Adjustment.
22.Drain transfer gearbox oil.See
MAINTENANCE ,
23.Remove 3 nuts securing intermediate silencer to
tail pipe.
24.Release silencer from mounting rubbers, remove
silencer and discard gasket.
25.Mark front and rear propeller shaft to transfer
gearbox flanges for reassembly purposes.
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MANUAL GEARBOX
9
REPAIR
26.Remove 4 nuts securing front propeller shaft to
transfer gearbox, release propeller shaft from
output drive flange.
27.Remove 4 nuts, release rear propeller shaft from
brake drum.
28.Remove 2 bolts securing clutch slave cylinder,
release slave cylinder and position aside.
29.Fit support plateLRT-99-007to gearbox jack.
30.Position gearbox jack and support plate to
gearbox and secure with 3 bolts.
31.Support the weight of gearbox.
32.Remove 4 nuts securing LH and RH mountings
to chassis and transfer gearbox mounting
brackets.
33.Remove bolts securing mountings to gearbox,
raise gearbox and remove both mountings and
heat shield from LH mounting and brackets.
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